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Air Brake Systems
If your vehicle has air brakes, it is important to get rid of
moisture in your system. Moisture will damage your
system if it is not removed daily.
There are two ways to do this. One is automatic through
the air brake vehicle’s air dryer with intregal automatic
moisture ejector that purges air from the system through
a self-contained reservoir. The other way to drain
moisture from the air brake system is to manually
activate drain valves at each reservoir. Drain the air
reservoirs occasionally to be sure the air dryer is
working properly.
Drain the air brakes at full system pressure. To be sure
you are at full pressure, check your air pressure
gage. It should read at least 100 psi (692 kPa).
Air Dryer
If your vehicle has air brakes, it will have an air dryer.
This collects and removes dirt, moisture, or other foreign
matter from the air prior to entering the brake system.
The dryer also acts as a moisture ejector. It
automatically ejects the moisture when the compressor
cycles. The purge tank has a manual drain valve
that must be drained every day. See “Air Brake
Systems” for the manual drain procedure. The air dryer
is mounted on the passenger side frame rail.
The dryer has a filter that you need to change at
intervals. SeeScheduled Maintenance on page 6-5for
more about servicing this filter.
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Electric Air Compressor
Your vehicle may have an electric air compressor. This
compressor is used to run options that require
pressurized air, such as air horn, air seat, 7.8L engine
exhaust restrictor, or 7.8L engine exhaust brake.
The air compressor is used when vehicles are not
equipped with an air brake system.
The air supply for this
system must be
maintained by releasing
the drain valve to eject any
moisture that may have
built up in the system.
It is recommended that this system be drained on a
weekly basis.
Clutch Pedal Free Travel
If you have a V8 engine and a manual transmission,
your clutch will need adjustment when pedal free travel
gets down to about 1/4 inch (32 mm), as measured
at the clutch pedal pad. You should have 1 1/2 to
2 inches (38 to 51 mm) of clutch pedal free travel.
If your clutch ever needs service, be sure to use only
GM clutch replacement parts.
Chassis Lubrication
Your Maintenance Schedule provides all of the required
chassis lubrication intervals and identifies proper
lubricants to use. Be sure to see your Maintenance
Schedule before performing any chassis lubrication
service. To determine location of chassis lubrication
items, use the following charts.
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Notice:If the jumper cables are connected or
removed in the wrong order, electrical shorting may
occur and damage the vehicle. The repairs would
not be covered by your warranty. Always connect
and remove the jumper cables in the correct
order, making sure that the cables do not touch
each other or other metal.
A. Heavy, Unpainted Metal Engine Part or Remote
Negative (−) Terminal
B. Good Battery or Remote Positive (+) and Remote
Negative (−) Terminals
C. Dead Battery or Remote Positive (+) TerminalTo disconnect the jumper cables from both vehicles, do
the following:
1. Disconnect the black negative (−) cable from the
vehicle that had the dead battery.
2. Disconnect the black negative (−) cable from the
vehicle with the good battery.
3. Disconnect the red positive (+) cable from the
vehicle with the good battery.
4. Disconnect the red positive (+) cable from the other
vehicle.
5. Return the positive (+) remote terminal cover to its
original position.
Rear Axle
When to Check and Change Lubricant
Refer to the Maintenance Schedule to determine
how often to check the lubricant and when to change it.
SeeScheduled Maintenance on page 6-5.
Notice:If you drive your vehicle through deep
water that is higher than the front or rear axle, water
may enter the axle housing and cause the axle
lubricant to break down. This could damage
the gears inside. Avoid driving your vehicle through
deep water. Jumper Cable Removal
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You should avoid driving your vehicle through deep
puddles or standing water. If you must drive through
water that is higher than the front or rear axle, see your
dealer immediately afterward to have the condition of
the axle lubricant checked.
How to Check Lubricant
Your vehicle may be equipped with one of the axles
shown above.
To get an accurate reading, the vehicle should be on a
level surface.
If the level is below the bottom of the filler plug hole,
located on the rear axle, you’ll need to add some
lubricant. Add enough lubricant to raise the level to the
bottom of the filler plug hole.
What to Use
Refer to the Maintenance Schedule to determine what
kind of lubricant to use. SeePart C: Recommended
Fluids and Lubricants on page 6-32. GL8 Axle
HD2 Axle
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Rear Axle Shift Motor
When to Check and Change Fluid
If you have an optional air-shift two-speed, controlled
traction, or locking differential type rear axle, a good time
to check the fluid level in the axle shift motor is when
the rear axle lubricant is checked. Use refrigerant
oil (shift motor only).
How to Check Fluid
Remove the plug on the front plate of the axle shift
motor, add enough fluid to raise the level to the bottom
of the filler plug hole, then replace the plug.
What to Use
Refer to your Maintenance Schedule to determine what
kind of lubricant to use. SeePart C: Recommended
Fluids and Lubricants on page 6-32.
Four-Wheel Drive
Transfer Case
When to Check Lubricant
It is not necessary to regularly check transfer case fluid
unless you suspect there is a leak or you hear an
unusual noise. A fluid loss could indicate a problem.
Have it inspected and repaired.
How to Check Lubricant
A. Fill Plug
B. Drain Plug
To get an accurate reading, the vehicle should be on a
level surface.
If the level is below the bottom of the fill plug hole,
located on the transfer case, you’ll need to add some
lubricant. Add enough lubricant to raise the level to
the bottom of the fill plug hole. Use care not to
overtighten the plug.
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When to Change Lubricant
Refer to the Maintenance Schedule to determine how
often to change the lubricant. SeeScheduled
Maintenance on page 6-5.
What to Use
Refer to the Maintenance Schedule to determine what
kind of lubricant to use. SeePart C: Recommended
Fluids and Lubricants on page 6-32.
Front Axle
When to Check Lubricant
It is not necessary to regularly check front axle fluid
unless you suspect there is a leak or you hear an
unusual noise. A fluid loss could indicate a problem.
Have it inspected and repaired.
Notice:If you drive your vehicle through deep
water that is higher than the front or rear axle, water
may enter the axle housing and cause the axle
lubricant to break down. This could damage the
gears inside. Avoid driving your vehicle through
deep water.
You should avoid driving your vehicle through deep
puddles or standing water. If you must drive through
water that is higher than the front or rear axle, see your
dealer immediately afterward to have the condition of
the axle lubricant checked.
How to Check Lubricant
To get an accurate reading, the vehicle should be on a
level surface.
If the level is below the bottom of the filler plug hole,
you may need to add some lubricant.
Add enough lubricant to raise the level to the bottom of
the filler plug hole.
What to Use
To determine what kind of lubricant to use seePart C:
Recommended Fluids and Lubricants on page 6-32.
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Noise Control System
Tampering with Noise Control
System Prohibited
The following information relates to compliance with
federal noise emission standards for vehicles with a
Gross Vehicle Weight Rating (GVWR) of more than
10,000 lbs (4 536 kg). The Maintenance Schedule
provides information on maintaining the noise control
system to minimize degradation of the noise emission
control system during the life of your vehicle. The noise
control system warranty is given in your warranty booklet.
These standards apply only to vehicles sold in the
United States.
Federal law prohibits the following acts or the
causing thereof:
1. The removal or rendering inoperative by any person,
other than for purposes of maintenance, repair or
replacement, of any device or element of design
incorporated into any new vehicle for the purpose of
noise control, prior to its sale or delivery to the
ultimate purchaser or while it is in use; or
2. The use of the vehicle after such device or element
of design has been removed or rendered inoperative
by any person.Among those acts presumed to constitute tampering are
the acts listed below.
Insulation:
•
Removal of the noise shields or any underhood
insulation.
Engine:
•
Removal or rendering engine speed governor (if
equipped) inoperative so as to allow engine
speed to exceed manufacturer specifications.
Fan and Drive:
•
Removal of fan clutch (if equipped) or rendering
clutch inoperative.
•Removal of the fan shroud (if equipped).
Air Intake:
•
Removal of the air cleaner silencer.
•Modification of the air cleaner.
Exhaust:
•
Removal of the muffler and/or resonator.
•Removal of the exhaust pipes and exhaust
pipe clamps.
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2. Push the release lever and slide the wiper assembly
toward the driver’s side of the vehicle.
3. Install a new blade by reversing Steps 1 and 2.
Other Service Items
Fuel Filter
Fuel Filter (Gasoline Engines)
The steel fuel filter is located near the engine
compartment on the driver’s side of the vehicle.
See your Maintenance Schedule for recommended
service intervals.
If your vehicle is equipped with the optional Davco
spin-on type filter, it is located on the driver’s side
frame rail.
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